The Two-striped Gartersnake typically has a single light stripe low on each side of the body but lacks the light stripe on top of the back which is present in most other gartersnakes found in California.

A medium-sized snake with a head barely wider than the neck and keeled dorsal scales.

Color and Pattern

Appearance is variable - there are two basic pattern morphs.
Both have a drab olive, brown, or dark gray ground color, with no dorsal stripe, except for a spot on the neck.

The striped morph has a yellowish to gray lateral stripe on each side, and a fairly uniform dorsal coloring, with only faint spotting.

The unstriped morph lacks the lateral stripes and has two rows of small dark spots on each side.
Light areas between the scales between these spots can create a checkered appearance (as seen in some of the pictures above.)

The underside is pale yellow or orange, unmarked, or with dark smudging.

A dark morph is found along the outer coast in San Luis Obispo County. A dark green and a reddish color morph occur along the Piru River in Ventura County. A melanistic population occurs on Catalina Island.

An adult T. hammondii was observed in an underwater ambush position about 15 cm below the surface, compressing its body into side-by-side loops while using its tail to anchor itself in stable aquatic vegetation. From this position it periodically quickly lunged forward at its prey. (Edward L. Ervin and Robert N. Fisher, Herpetological Revies 38(3), 2007.

Breeding

Breeding has been observed in late March and early April, with live young born in late July and August.

Habitat

Generally found around pools, creeks, cattle tanks, and other water sources, often in rocky areas, in oak woodland, chaparral, brushland, and coniferous forest.

Geographical Range

Ranges continuously from near Salinas in Monterey County south along the coast mostly west of the south Coast Ranges, to southern California where it ranges east through the Transverse Ranges (and into the desert in Victorville) and south through the Peninsular Ranges into northern Baja California. Occurs in southern Baja California in isolated areas.
Also occurs on Catalina Island.

Elevational Range

At elevations from sea Level to 6,988 ft. (2130 m).

Notes on Taxonomy

Formerly classified as a subspecies of Thamnophis couchii. T. digueti was synonymized with T. hammondii by McGuire and Grismer (1993, Herpetologica 49:354-365).

The Santa Catalina population of T. hammondii is treated as a distinct subspecies by the California Dept. of Fish and Game - Santa Catalina garter snake, Thamnophis hammondii ssp.

Wright, Albert Hazen & Anna Allen Wright. Handbook of Snakes of the United States and Canada. Cornell University Press, 1957.

Conservation Status

The following status listings are copied from the April 2018 Special Animals List and the 2017 Endangered and Threatened Animals List, both of which are published by the California Department of Fish and Wildlife.

If no status is listed here, the animal is not included on either CDFW list. This most likely indicates that there are no serious conservation concerns for the animal. To find out more about an animal's status, you can go to the NatureServe and IUCN websites to check their rankings.

The 2017 Special Animals List lists the population on Santa Catalina Island as a separate subspecies, Thamnophis hammondii ssp. - Santa Catalina garternake. This listing for this snake is shown below.

This is the listing for Thamnophis hammondii - two-striped gartersnake:

Organization

Status Listing

NatureServe Global Ranking

G4

Apparently Secure—Uncommon but not rare; some cause for long-term concern due to declines or other factors.

NatureServe State Ranking

S3S4

Vulnerable—Vulnerable in the state due to a restricted range, relatively few populations (often 80 or fewer), recent and widespread declines, or other factors making it vulnerable to extirpation from the state.

Apparently Secure—Uncommon but not rare in the state; some cause for long-term concern due to declines or other factors.

U.S. Endangered Species Act (ESA)

None

California Endangered Species Act (CESA)

None

California Department of Fish and Wildlife

SSC

Species of Special Concern

Bureau of Land Management

S

Sensitive

USDA Forest Service

S

Sensitive

IUCN

LC

Least Concern

This is the listing for Thamnophis hammondii ssp. - Santa Catalina garternake:

Organization

Status Listing

NatureServe Global Ranking

G4T1

The species is: Apparently Secure—Uncommon but not rare; some cause for long-term concern due to declines or other factors.

This subspecies is: Critically Imperiled—At very high risk of extinction due to extreme rarity (often 5 or fewer populations), very steep declines, or other factors. Imperiled—At high risk of extinction due to very restricted range, very few populations (often 20 or fewer), steep declines, or other factors.

NatureServe State Ranking

S1

Critically imperiled in the state because of extreme rarity (often 5 or fewer populations) orbecause of factor(s) such as very steep declines making it especially vulnerable to extirpation from the state.